Friend's brother is ignoring me because I like him and there is an age difference between us. What do I do?

I have a really close friend , She is perhaps one of my best friends. But every time I'm with her i think of her brother.He's the problem. She has no problem at all with me liking him well except she calls it gross and you know the family thing. We just laugh it off. Her brother is older than us by a couple of years also so she tells me he wants someone his age.

Well, her brother and I became extremely close to an extent i could say i love him. We talked practically every day and night. I dreamed about him. Well it turns out he liked my other friend , which hurt me very badly because she knew how i felt. I confronted him about it and he said "Well we weren't dating so i thought it wouldn't be a big deal." But he knew how i felt towards him. Now I still talk and hang out with his sister. I also don't want to avoid him because I love him enough that I would still love being just a friend. But now he's ignoring me and giving me the cold shoulder. He won't talk to me unless we're in a group of people. I feel left alone and hated because of him. But all i want to is be his friend at least.I heard "Love knows no age", but that simply isn't how he feels. But just because I'm younger , he can simply ignore me? He knows I'll never hate him or be rude towards him. What should i do? Please help! Thank you.